1. Field of the Invention
This invention relates to gas stream monitoring apparatus and particularly to such apparatus for use with gas cooled dynamoelectric machines.
2. Description of the Prior Art
Large dynamoelectric machines occasionally fail due to thermal degradation of various materials, particularly organic insulation. Since an early detection of the insulation failure is essential to the prevention of a large scale burnout of the dynamoelectric machine, monitoring devices are desirably used which monitor the gas streams that flow through dynamoelectric machines. Presently, most monitors work by detecting particulates in the gas stream, which are found when insulation is being thermally degraded. When the monitor detects degradation products and generates a signal, the flow of the detectable particulates to the monitor is terminated to determine whether the signal is genuine or is due to a malfunction of the monitor. If the signal then terminates it is assumed to be genuine and the generator can be shut down for repair or other precautions taken.
Since down time on a large generator can be costly, it is normally important to locate the insulation failure and repair it quickly. Over 50 different materials are used in generators, including regular and modified expoxies, polyesters, silicones, phenolics, etc., and unless the failure is easily visible, it may be very difficult to locate.
In U.S. Pat. No. 3,972,225, issued Aug. 3, 1976, it was disclosed that if the gas stream is sampled when the monitor indicates that a failure is occurring, the products collected can be analyzed to determine which material in the generator was failing. Since the location of the various material is known, the search for the failure is considerably shortened.
It was also disclosed that the sampling can be done automatically, so that when the monitor produces a signal it can check for authenticity and the sample taken without human interference.
Finally it was disclosed that a particular sampling device, which separates the products of the gas stream into particles 10 microns or greater, particulates less than 10 microns, and vapors and gases, is particularly useful in facilitating the analysis.